sub report recordsource (Access 2000)

In the past I have been able to set the recordsource of a report depending on how I reach the report or what chocies have been made before the report is run. It works great. Now I need to set the recordsource of a subreport and am getting error messages:
If I try to change the recordsource in the subreport I am told that you cannot change the recordsource once the report has strated printing. That makes sense.
So, I tried setting the recordsource in the main report and get the following error message:
See attached Word doc. I am showing the code in the same document.